In the past, in a video camera capable of carrying out comparatively advanced operations for business purposes or the like, a lens housing is provided with a focus ring for moving the position of a focus lens. The focus ring is rotated manually to adjust focus as needed, and the focus lens can be moved forward and backward along an optical axis based on a rotation amount of the focus ring.
In this case, the focus ring does not directly, mechanically work with a focus lens driving mechanism. The rotation amount of the focus ring is electrically detected to drive a motor, thereby moving the lens through the focus lens driving mechanism. That is, there is provided an encoder that detects the rotation amount of the focus ring, and the rotation amount detected by the encoder is changed into a signal and transmitted to the motor to drive the focus lens via the motor. Hence, the focus ring may not have a fixed end and can be endlessly rotated in either of clockwise and counterclockwise directions without restriction. With a structure that is not provided with such fixed end, for example, while automatically carrying out a focus adjustment with an autofocus function, a focus-adjusted state can be corrected in a simplified manner by manually rotating the focus ring without limitation.
For example, in Japanese Unexamined Patent Application Publication No. H8-146282 published by the Japan Patent Office, there is a disclosure of a focus ring uncoupled from a scale ring at automatic focusing to prevent the focus ring from being rotated.
In the case of a structure having no fixed end on the focus ring, there is an advantage in that focus correction can be comparatively easily carried out at automatic focusing, however, it has been required to confirm a degree of focused state in the automatic focusing on a display of a finder. In the case of a lens of a type having a focus ring with a fixed end, a rotated position of the focus ring corresponds to a focus-adjusted state (focal distance) and accordingly adjustment in manual operation can be carried out easily, however, the focus ring with the fixed end should be rotated in agreement with the focus-adjusted state at automatic focusing and therefore, there is a problem that a mechanism of rotating the focus ring is complicated.
In addition, in the case of using an autofocus function, there is a limitation in rotational speed of a motor and therefore, there is a difficulty in focusing at a speed higher than the rotational speed of the motor.
The present invention has been made in view of the above and intends to perform a suitable operation both at automatic focusing and at manual focus adjustment.